Cathode ray tubes with target screens and the manufacture thereof

ABSTRACT

Point light sources and elongated light sources are disclosed which comprise light pipes in the form of elongated and funnel shaped transparent scintillators. To increase the intensity of the light at the exit terminal of the light pipes, they have tapered sides where the thickness increases in the direction of the exit terminal. Application of these light sources to the photo-fabrication of line-screen and dot-screen cathode ray tubes is disclosed.

United States Patent 1 1 Goodman 1 Apr. 2, 1974 CATHODE RAY TUBES WITHTARGET SCREENS AND THE MANUFACTURE THEREOF [76] Inventor: David M.Goodman, 38 Debra Ct.,

Seaford, NY. 11783 [22] Filed: Aug. 12, 1970 [21] Appl. No.: 63,331

Related U.S. Application Data [62] Division of Ser. No. 772,639, Nov. 1,1968, Pat. No. A

[52] U.S. Cl 250/365, 250/368, 250/458 [51] Int. Cl. G01] 39/18 [58]Field of Search... 240/41.35 R, 41.35 C, 41.37, 240/1 EL, 2.25; 95/];250/71, 461, 227, 366, 368, 504, 505, 365; 313/65 LP [56] ReferencesCited UNITED STATES PATENTS 2,213,868 9/1940 Lucian 240/2.25 X

2,225,439 12/1940 Arens et al. 240/2.25 X 2,897,388 7/1959 Goodman313/65 LF 3,282,176 11/1966 Morse et al 95/1.l 3,437,804 4/1969 Schaeferet a1. 240/4L35 R 3,439,157 4/1969 Myles 240/1 EL 3,587,417 6/1971Balder et al 95/1 R Primary Examiner-James W. Lawrence AssistantExaminer-Harold A. Dixon Attorney, Agent, or FirmAnthony A. OBrien [57]ABSTRACT Point light sources and elongated light sources are disclosedwhich comprise light pipes in the form of elongated and funnel shapedtransparentscintillators. To increase the intensity of the light at theexit terminal of the light pipes, they have tapered sides where thethickness increases in the direction of the exit terminal. Applicationof these light sources to the photofabrication of line-screen anddot-screen cathode ray tubes is disclosed.

29 Claims, 10 Drawing Figures CATHODE RAY TUBES WITH TARGET SCREENS ANDTHE MANUFACTURE THEREOF CROSS REFERENCES TO RELATED APPLICATIONS This isa division of U.S. Pat. application Ser. No. 772,639 filed Nov. 1, 1968now U.S. Pat. No.

This application is a continuation-in-part of my copending U.S. Pat.application Ser. No. 85,353 filed Jan. 27, 1961 entitled Target Screensfor Cathode Ray Tubes and the Like (now U.S. Pat. No. 3,691,424) whichis a division of my then copending U.S. Pat. application Ser. No.800,854 filed Mar. 20, 1959 now U.S. Pat. No. 3,081,414 granted Mar. 12,1963 entitled Wide Band Cathode Ray Tribes and the Like. U.S. Pat.application Ser. No. 800,854 in turn was a continuation-in-part on threeof my previously copending U.S. Pat. applications, Ser. No. 514,973filed June 13, 1955 now U.S. Pat. No. 2,885,591 entitled Cathode andDirected Ray Tubes and U.S. Pat. Ser. No. 522,609 filed July 18, 1955now U.S. Pat. No. 2,897,388 entitled Directed Ray Tube and the Like andU.S. Pat. Ser. No. 448,039 filed Aug. 5, 1954 now U.S. Pat. No.2,897,398 entitled System for Selected Transmission, Storage, Display,Coding or Decoding of Information." The instant application also is acontinuation-in-part on my copending U.S. Pat. applications Ser. No.345,197 filed Feb. 17, 1964 entitled High Sensitivity Beam-Index andHeaterless Cathode Ray Tubes" which is incorporated by reference; andU.S. Pat. Ser. No. 488,017 filed Sept. 17, 1965 entitled Systems forModulation of Beam-Index Color Cathode Ray Tubes, and the Like" now U.S.Pat. No. 3,564,121.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to target screens used with beam-index cathode ray tubes. Inparticular, it relates to target screens used with beam-index colorcathode ray tubes (color kinescopes) and improved methods of manufacturethereof.

2. Description of the prior art it has long been recognized by personsfamiliar with this art that the cathode ray tube of the beam-indexvariety can be used as an extremely versatile tool. Especially in thefield of color television, it has been long recognized that thebeam-index cathode ray tube has many potentially advantageous features.Among these advantageous features is the possible reduction of thenumber of electron guns from three in present day commercial color tubesof the shadow-mask variety to one gun in a beam-index tube; and thefurther elimination of the apertured mask and frame assembly, retainingclips, and studs, etc. In addition to the savings on the cost of theseparts, there is also advantage derived from the'beam-index in that iteliminates the need for precise alignment of the three electron beamswith the thousands of holes in the aperture mask. Furthermore, theseholes must be aligned with the thousands of trios of phosphor dots onthe target screen which requires that the shadow-mask assembly bemarried" to its faceplate which introduces another complicating factorin the production of tubes of this type. Additionally, the beam-indextube generally is considered capable of eliminating the costlyconvergence circuits and assemblies, and the de-gaussing coil andcircuits, now considered standard requirements in color televisionreceivers.

The beam-index tube also promises to make possible many improvements inpackaging and styling. This includes the construction of very smallpersonal size television receivers; the construction of wide angledeflection systems; kinescopes with shorter neck length; and theconstruction of lighter-weight glass envelopes, with greater use of itsfaceplate area for imagedisplay.

Still further, it has been predicted (and experiments by applicant haveconfirmed) that the greater efficiency of the beam-index tube permitsoperation of the target screen at lower voltages than the shadow-masktype of color tube. The result of this lower operating voltage coupledwith the removal of the shadow-mask assembly is that the generation ofx-radiation is reduced in a beam-index receiver to the point where theproblem becomes no more severe than in a monochrome set. Power supplycosts also are reduced.

Nevertheless, despite these many significant advantages in economy,esthetics, and health physis the beam-index color tube is not currentlyin commercial production, not in this country nor elsewhere. One of thereasons for this situation is that the construction of a line-screenbeam-index color kinescope on a production basis can introduce a costsavings which is not sufficiently favorable to induce presentmanufacturers to abandon their very large investment in productionfacilities now geared to make color kinescopes of the shadow-maskvariety.

Some of the difficulties in making line'screen beamindex colorkinescopes have been long recognized. Numerous solutions have beenoffered by many skilled workers in this art. Thus, applicants ownteachings in US. Pat. Ser. No. 514,973 (now U.S. Pat. No. 2,885,591 aredirected to this subject. Therein, appli cant teaches (l) the use ofrollable phosphor screens which are mass produced and later insertedinto the envelope of the tube, and (2) the use of an electricallyconducting mesh which replaces the conventional elec tron transparentaluminum layer. in U.S. Pat. Ser. No. 522,609 (now U.S. Pat. No.2,897,388) applicant describes a plurality of target screens forbeam-index kinescopes for color television. These target screens containstrips of red, green, and blue color-emitting phosphors in register withindex-signal generating strips. The index signals may be in the opticalor in the x-ray region of the spectrum. More than one type of indexsignal may be used. The index-generating elements may be admixed withthe color producing phosphors.

In U.S. Pat. Ser. No. 800,854 (now U.S. Pat. No. 3,081,414) which was acontinuation-in-part on the two applications just identified, applicantdiscloses a plurality of target screens for beam-index color kinescopes.These screens include a mesh-like structure which is used in conjunctionwith strips of color producing phosphor materials wherein selectedstrands of l the mesh also serve to provide the index signals. Thedisclosure relating to target screens is carried forth into applicantscurrently copending U.S. Pat. application Ser. No. 85,353 filed Jan. 27,1961.

In U.S. Pat. Ser. No. 212,612 filed July 26, 1962 (now abandoned andrefiled as U.S. Pat. Ser. No. 562,031 on June 2, 1966) applicantdiscloses a beamindex and heaterless color kinescope comprising a fourlayer target screen. The fourth layer is deposited on top of the indexstrips to suppress the effects of ion bombardment. Also, in thatapplication which matured into U.S. Pat. No. 3,567,985 spiral shapedscintillators are shown positioned adjacent the funnel section ofcathode ray tubes.

In U.S. Pat. Ser. No. 345,197 filed Feb. 17, 1964 applicant disclosestarget screens for beam-index, heaterless, and color cathode ray tubeswhich comprise optical fibers positioned across the faceplate of thetube. These fibers, in one embodiment, scintillate in response toelectron excitation. Non-scintillating fibers or filaments are alsodisclosed which have phosphors associated therewith for providingoptical signals in response to excitation by the electron beam. Also,index signal producing phosphors are described as being embedded in thefaceplate of the tube.

In U.S. Pat. Ser. No. 488,017 filed Sept. 17, 1965 applicant disclosestarget screens with x-ray generating beam-index elements which arecomprised of low atomic weight materials to make them more easilydistinguishable from the color producing phosphors.

As to the prior art of others in the field of beam-index colorkinescopes, reference is made to Saulnier U.S. Pat. No. 3,367,790 filedDec. 1, 1964 and granted Feb. 6, I968 (assigned to the Radio Corporationof America) entitled Method of Making Color Kinescopes of theLine-Screen Sensing Variety. Saulnier describes at Columns 1 and 2 thedifficulties of screen fabrication experienced by workers in this fieldas follows:

As is well known, the brightness of an image produced on any televisionscreen is greatly enhanced when the screen is metallized, i.e., when itis provided on its rear surface with a particular metal layer.Metallized phosphor-screens of the abovedescribed sensing varieties,however, have certain disadvantages. These disadvantages resultprimarily from the fact that, although the usual specular metal layer istransparent to electrons, it is nevertheless substantially opaque notonly to (a) the invisible rays emitted by the signal-generatingmaterial, but also to (b) the visible or invisible actinic rays employedin the coventional photographic method of laying-down the line-likemosaic pattern or patterns of which the screen is comprised.

Because, as above mentioned, a conventional electron-transparentspecular metal layer is opaque to the invisible (e.g., ultra-violet)control or reference signals, if such a layer is laid down on asensing-type screen of the kind where the signal-generating indicia andthe light-generating phosphor lines comprise but a single layer, thenthe photocell or other pick-up" device for the control signals must bemounted in front of the screen-plate. This front mounting is undesirablebecause the reference signals may be contaminated by ambient rays beforethey reach the pick-up device. Furthermore, the very presence of thepick-up device in front of the kinescope limits the angle from which thescreen may be viewed.

Because prior art tubes that contain a sensing screen having more thantwo layers (see Law U.S. Pat. No. 2,633,547) employ a pick-up devicemounted at the rear of the screen they are not subject to theabovedescribed disadvantages of sensing tubes that contain a two-layerscreen. Multi-layer sensing screens however are more expensive tomanufacture than two-layer sensing screens. This is so principallybecause in multilayer sensing screens the specular metal layer, whichcomprises the substrate for the signal-generating strips, is opaque tothe actinic rays used in the now standard photographic method of formingsaid strips on the metal. As a consequence, the bulb that is to containthe finished screen must be made in two precisely matched parts (i.e.,cone and cap) to permit the optical stencil and light source to bedisposed adjacent to the rear surface of the metal layer during thephotographic deposition process.

If the several photographic exposures required in laying down amulti-layer sensing screen could all be made with the appropriateoptical stencil and light source disposed adjacent to the obversesurface of the face-plate it would then be practical to employ aone-piece" envelope or bulb (as in a black-and-white kinescope) and thusto effect economics not only in bulb costs but in the photographicprocess as well. To this end, it has previously been proposed to makethe aluminum layer so thin, and the exposure time so long, that theactinic rays required in laying down the sensing strips will penetratethe aluminum (or other specular metal) layer. But such obviousexpedients are incapable of practical achievement because the reductionin the thickness of the aluminum layer required to make it permeable toradiation of an intensity useful in the photo-deposition process reducesthe electrical conductivity and reflectivity of the specular metal tounusable values.

The foregoing and other less apparent disadvantages of present daytwo-layer and three-layer sensingscreens are obviated, in accordancewith the present invention, by the combination, with any suitabletransparent or translucent phosphor substrate, or aspecular metal layerof a thickness normally rendering it substantially opaque to (a) theinvisible rays from which the control signals are derived and (b) thevisible or invisible actinic rays employed in the screen-plottingoperation, yet transparent to electrons, and containing openings in anumber and a size sufficient to render said metal layer or certain partsthereof at least 10 percent transparent (and in some cases as high as 25percent) to such visible and invisible rays. The invention may be saidfurther to reside in the later described methods of achieving specularmetal layers of a foraminous (crazed or perforate) nature.

Thus, Saulnier proposes to overcome some of the difficulties previouslyexperienced by providing the target surface of a phosphor screen with apartially transparent specular metal layer. A process for doing thisrequiring several additional steps in the manufacturing process is thesubject of his invention. Thus, it is clear that the construction ofline-screen beam-index color kinescopes has attracted expert attention.And, although it has been the subject of much research and developmentin this country and abroad there remains room in this technology forsubstantial reduction in the cost of manufacture of these cathode raytubes.

SUMMARY OF THE INVENTION Accordingly, the purpose of this invention isto reduce the cost in manufacture of line-screen beam-index cathode raytubes in general and beam-index color kinescopes in particular. Theinvention resides in new beam-index target screen structures and methodsof construction thereof. In one aspect of the invention the targetscreen is provided on its inside surface with ribs, projections, orother indicia which are used as fiducial markers to simplify theregistration of the color producing strips with the index signalproducing strips. These ribs or indicia may be molded with the faceplateof the tube or they may be supported on the faceplate at a later stagein manufacture.

In another aspect of this invention, an elongated or ribbon lightsource, derived from a transparent sheet of scintillator material, isused in a lighthouse to increase the speed of production whenphotoresist methods are used to deposit the phosphor strips. The sheetof scintillator is excited over a large surface to improve its capturearea, thereby permitting large sources of ultraviolet excitation to beused. In modified form, this same type of scintillator sheet can be usedto replace the point" source of light conventionally used in prior artmethods of screen construction by the photo method. Ths invention alsoteaches the use of servocontrolled printing techniques for laying downthe line screen wherein the ribs, projections, or other indicia of thetarget screen are employed to guide the brushes or jets used in thescreen printing process.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 depicts a cathode ray tube in acabinet with an index signal detector feeding optical index signals intoa chasis located beneath the tube.

FIG. 2 is a front view, enlarged, of the target screen on the inside ofthe faceplate of the tube of FIG. 1.

FIG. 3 is a cross-section of a typical target screen and faceplate.

FIG. 4 also is a cross-section of the target screen and faceplate, withan aluminum layer on the back of the phosphor strips.

FIG. 5 illustrates a roller for scraping (or coating) the rearwardlyfacing edge of index signal supporting ribs or filaments.

FIG. 6 illustrates a conventional light source, and alternatively anovel elongated scintillator light source, positioned on the outside ofthe faceplate for activating or polymerizing selected photosensitivemixtures or layers in the process of target screen construction.

FIG. 6A illustrates, in cross section, a rib or projection on the insideof the target screen which is molded integrally with the faceplate.

FIG. 7 illustrates a method of painting the phosphor strips directly onthe faceplate. A plurality of brushes for producing one color triad andone index strip are shown guided by ribs or projections on thefaceplate.

FIG. 8 is akin to FIG. 7 except that the guide pins for the phosphorbrushes are positioned against both the ribs and the faceplate of thetube. Alternatively, an optical or electrical indicia sensingservo-control system is depicted for guiding the phosphor brushes orjets.

FIG. 9 illustrates the scintillator light source of FIG. 6 with its exitregion at the focal point of a lens system. Also shown is a hollowfunnel scintillator for providing a point light source.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 a beam-index cathoderay tube (CRT) is shown with a faceplate 11 having a target screen 10.The faceplate has an implosion panel 8 bonded thereto by a thin resinlayer 9. One form that the target screen may take is shown in FIG. 2,greatly enlarged, and is comprised of an array of index signalgenerating elements disposed in register with an array of differentcolor producing phosphors 12B (blue, 14R (red), and 166 (green).Ordinarily, but not necessarily, the electron beam from gun 7 of the CRTscans the phosphor strips at right angles in order to develop a colorimage suitable for viewing. The signals generated by the index stripsare detected in the scintillator 6 thereby generating optical indexsignals which are converted into electrical signals by photodetector 5.A plurality of windows 2 are provided for scintillator 6 in the opaqueelectrically conductive aquadag coating ordinarily deposited on theinside of the CRT funnel section. This coating (which alternatively maybe of aluminum) is used to establish a uniform electric field inside thetube. To help keep stray light out of the scintillator and thephotodetector, the CRT is housed in a cabinet 4 containing a chassis 3which houses the photodetector 5. The index signals, and the opticalindex signals derived therefrom, generally are used to indicate theposition of the electron beam on the target screen. For color televisionreceivers these index signals are used to control the sequentialexcitation of the different color producing phosphor strips.

FIG. 3 is an enlarged view of section 3--3 taken through the targetscreen of FIG. 2. Glass faceplace or substrate 11 has deposited on itsinside surface the blue, red, and green color producing strips 128, 14R,and 16G separated by ribs or projections 18. Associated with these ribsare the index signal generating elements. Projections 18 may also bestrands ofa mesh- Iike structure as disclosed in applicants co-pendingU.S. Pat. applications Ser. No. 85,353 and U.S. Pat. Ser. No. 345,197,supra. The resin layer 9 and implosion panel 8 of FIG. 1 are alsoillustrated in FIG. 3. In one embodiment rib 18 is optically andmechanically continuous with faceplate 11. This is illustrated at 17. Itis preferred in this case that the ribs 18 be molded at the same timethat the front panel is pressed. In this embodiment, index signalgenerating element 21 is shown supported on rib 18. Typically, element21 is the phosphor designated P-l6 which emits radiation in theultraviolet peaking at about 3,800 Angstroms. In another embodiment, rib18 may be secured to the faceplate after it is pressed as shown at 19.In this case, the rib 18 may be comprised of material selected from oneof the electron-sensitive scintillating glasses. Hence, no additionalelement akin to 21 is shown at 19. If the scintillator rib is opaque orabsorptive of its own radiation, then detection of the index signal besttakes place rearwardly of the screen as by scintillator 6 of FIG. 1. Ifthe rib is transparent to its own radiation, however, the index signalsmay be light piped to an edge of the target screen as set forth inapplicants U.S. Pat. Ser. No. 485,017. In FIG. 3, the ribs 18 are inregister with the color producing phosphor strips and physicallyseparate the strips into triads. The ratio of color strips to indexstrips can be varied from the 3:1 relationship illustrated and more thanone index signal generating material can be used.

In FIG. 4, a target screen akin to that in FIG. 3 is shown. An electrontransparent, electrically conductive, light reflective aluminum layer 22is disposed on top of the color producing phosphors 12B, 14R, and 16G toincrease the brightness when high voltages are used on the targetscreen. When a scintillating glass transmissive of its own radiation isused for rib 18 the aluminum layer may extend over the rib as depictedat 25. In this case, the optical index signals are transmittedtransversely of the faceplace 11 through rib 18 to a suitable exitterminal. When a scintillating glass is not used, or for other reasons,layer 22 may also cover the rib 18 as depicted at 24. In this case, toradiate index signals rearwardly index signal generating element 23 isdeposited on top of layer 24. Alternative embodiments are shown by ribs27 and 27 Rib 27 does not physically separate the color producingphosphor strips into triads as do ribs 18 but is supported by one of thestrips. Also, rib 27 straddles a pair of color producing strips; and maybe disposed rearwardly of the aluminum layer 22.

FIGS. -8 illustrate different methods of constructing the target screensof FIGS. 3 and 4. Thus, in FIG. 5 an array of three different colorproducing phosphor strips is shown on the faceplate 11. Using the wellknown photo-resist method the phosphors can be mixed with phtoo-sensitvecarriers to form a slurry or, alternatively, the phosphors can be dustedon or otherwise applied after a photo-sensitive layer is deposited andexposed. Exposure of the photo-sensitive material can be through thefaceplate 11, or from the inside thereof. Three successive series ofsteps are involved, one series for each color. The layer must beapplied, exposed with careful registration of an optical master, andthen developed to remove the unhardened material. Ordinarily, in makinga screen for a shadow-mask tube the faceplate is rotated and tilted toapply the photo-sensitive layer. This rotating motion should be changedto a reciprocating motion so that the ribs 18 do notinterferc with thesmooth application of the photo-sensitive layer. If the ribs are appliedafter the color phosphors are deposited the slurry can be rotated andtilted. The next step is to lay down the index material, akin to 21 ofFIG. 3 or 23 of FIG. 4. In a three layered screen this can be adifficult and tedious task as attested to by Saulnier and by applicantsown experience. Also, in a conventional three layered screen the indexstrip is deposited last so that any imperfection in this step is veryexpensive. It wastes the time and effort involved in laying down thethree phosphors and the thin aluminum layer. To avoid thesedifficulties, and therefore to increase production yield, this inventioncalls for the direct application of the index phosphor to the raisedrib. Thus, roller 26 in FIG. 5 depicts the mechanical application ofindex phosphor to the ribs 18. This is a simple but extremelyadvantageous use of this aspect of the invention. Note that althoughaluminum layer 22 is not shown in FIG. 5 it may be used if desired andis best applied before the use of the roller coating.

In FIG. 6, a photographic technique is illustrated for depositing theindex strips. This may be desirable when the curvature of the faceplate,or some other consideration, rules out the use of the mechanicalapplication of the index phosphor. The photo-sensitive layer may beapplied to the ribs 18 by spray or slurry or it may be otherwisedeposited. Radiation from ultraviolet source 28 is transmitted throughthe front of the panel, or it may come from the rear to polymerize thephotosensitive layer. The two advantages in exposing from the front, asshown, are that (1) the color producing phosphor strips attenuate theultraviolet light and (2) the layer next to the glass polymerizes first.Item (1) helps keep index material off the color phosphor region of thescreen (if necessary, a temporary yellow dye can be added to the colorphosphors to further suppress the blue and ultraviolet transmission) anditem (2) provides for better adhesion of the phosphors to the faceplateand less criticality in exposure time. Another advantage of frontalexposure, in fact the greatest advantage when the photo-resist processis used for screen deposition, is that the faceplate and funnel sectioncan be joined by flame sealing prior to screen construction. Thiseliminates the need for frit-sealing which is very slow and may run asmuch as four hours; and it eliminates the need for (and costs incurredin) grinding the glass surfaces which are to be frit sealed.photoapplication substantially Thus, the use of the raised rib 18,whether for direct application of the index phosphor or -forphotoapplication of the index phosphor, substantially improves theprocess of making beam-index target screens for color kinescopes.

A special consideration arises when the photomethod is used from thefront of the faceplate and this I will be explained with respect to FIG.6 taken in conjunction with FIG. 6A and FIG. 4. In FIG. 4 the colorproducing triads 12B, 14R, 16G are affixed to the faceplate. aluminumlayer 22 is on top of the color triads; and is on top of rib 18 asdepicted at 24. The question arises as to how the radiation fromultraviolet source 28 (FIG. 6) can penetrate the aluminum layer 22 so asto harden the photo-resist to secure index material 23 to the top ofaluminum layer at 24.

There are a number of answers as follows: First, I have discovered bydirect observation, and Saulnier confirms that a smooth and continuousaluminum layer as conventionally applied to a CRT screen has a degree oftransparency. This means that with sufficient exposure time andintensity of illumination the index phosphor 23 can be affixed on therearward side of the aluminum layer 22. Second, the aluminum layer canbe scraped off the rib by a suitable abrasive or polishing tool. Andthird, as depicted in FIG. 6A the rib 18 can be contoured or sharpenedto cause the aluminum layer 22 to break at the region where indexphosphor 23 is to be applied.

It is desirable, in any event, to increase the intensity of radiationused in the photo-resist process. Fre quently, to deposit the coloremitting phosphors by this process in a shadow-mask tube a IOOQ watthigh pressure mercury are light source is used. This type of mercury arcgenerates ultraviolet and blue-white visible radiation for exposure ofthe photo-resist through the apertures in the shadow mask. Specialquartz optics are used to concentrate the light. The overall efficiencyis low and water cooling is required to remove the heat which isdissipated. This source of light requires several minutes for properexposure. The exposure must be repeated for each color phosphor, orindex strip, that is deposited by the photo-method. In large volumeproduction this is a very time consuming and expensive operation.

In this invention, the linear shape of the phosphor strips to bedeposited and the unique properties of plastic scintillators arecombined to reduce exposure times. Thus, ultraviolet light source 28 isshown in FIG. 6 in cylindrical form surrounded by a specially shapedplastic scintillator 29. Space is provided between the scintillator andlamp for air cooling. For example, a thin sheet of scintillator materialcan be bent to surround light source 28 so that opposite edges of thesheet meet as depicted in the drawing. The ultraviolet radiation frommercury vapor lamp 28 strikes the side walls of sheet 29 and causes itto scintillate internally. The optical radiation thus generated istransmitted by internal reflections in scintillator 29 to exit terminal30. Terminal 30 thus constitutes an elongated or ribbon light source andis positioned parallel to the strips of the target screen. To appreciatethe advantages gained by this arrangement in reducing exposure time fromthat required with a point source of light typical dimensions of thecombination of FIG. 6 are cited as follows: the faceplate 1 1 is 12inches high, as is the scintillator sheet 29. The thickness of sheet 29is approximately 0.015 inches. The resultant light source is 12 X0.030inches. This represents an improvement of 12/0030 or 400 over apoint source of light measuring 0.030 X 0.030 inches. Evidently, thelarger the screen and the longer the light source, the greater is theimprovement.

Mercury vapor lamp 28 canbe high pressure or low pressure and it can beshort wave or long wave. Scintillator 29 is available from NuclearEnterprises, San Carlos, California, and can be identified as theirNE-l02 and NE-lll. Alternatively, reference is made to Hyman U.S. Pat.No. 2,710,284 for details on plastic scintillators. The quantumefficiency of these scintillators approaches 100 percent. The light lossthrough the side walls is acceptable. But even at that, a second layertransmissive of its own scintillations, such as 31, can be used torespond to and capture the radiation from the side wall of 29. The lightloss through internal reflections is low. Finally, the scintillations ofNE-103 are blue-white which means its transmission through the faceplateof ordinary CRT glassis high, and its ability to polymerize thephoto-sensitive medium is good. Therefore, a much improved light sourceis provided for making strip-like target screens.

A number of variations in the light source and its use are describedwith reference to the drawings. In FIG. 6 light emitting strip 30 is onthe outside of the faceplate ll, is adjacent thereto, and is in linewith rib 18 which supports the photo-sensitive material. Light emittingstrip 30 can be stepped along the faceplate to be in register with eachrib 18 in sequence, or it can be placed at a distance from the faceplateto expose the resist through mask 60. In the latter case, openings 61 inthe mask 60 may be provided in register with the ribs 18. These openingsare displaced from the ribs depending upon the distance that separatessource 28 from faceplate 11. The arrangement shown is for so calledparallel light input. The best mode however from the point of view ofreducing exposure times is to provide a plurality of light emittingstrips adjacent to the face plate with one light emitting strip inregister with each strip of photo-resist to be illuminated. This can bedone by having a plurality of scintillator sheets akin to 29 formed intoajig or fixture which mates with the surface of the faceplate. Thesheets can be stacked, like pages spread in an open book, to receive theinput radiation over a broad surface thereof. FIG. 9 shows light strip30 to the focal point of a lens system. The output of the lens issubstantially parallel light. The light source of FIG. 9 can provide alarge area collimated beam to irradiate the entire faceplate area; or itcan be made smaller and positioned closer to the faceplate on the targetscreen. Lastly, a funnel shaped plastic scintillator 51 is illustratedin side view in FIG. 9 with an exit region 52 corresponding to a pointsource. The scintillator 51 may surround the primary light source, akinto the arrangement of 29 and 28 or it may be excited by radiation whichenters via opening 51 in the funnel, or it may be otherwise excited.Preferably, the funnel wall is tapered slightly to increase in thicknessat the exit region 52. The hole in the funnel at 52 should be closed toprovide the maximum concentration of light output. Suitable primarysources of excitation are the type A-l hig p essym e y r amps supp i byt Zenith Radio Research Corporation (having an are discharge length ofapproximately 1 inch) and the type B116 high pressure mercury arc lampof thgGeneral As desirable as the foregoing arrangements are, it will benoted that except for the direct application of index phosphor by theroller process of FIG. 5 they all involve the photo process. This is ahighly developed art and the photo process produces extremely usefulresults. But, it is slow, critical as to exposure, and consumes muchproduction time. Furthermore, the depositions of the phosphor strips aresequential so that if the last deposition is defective the productionresults previously achieved are of no lasting benefit. Accordingly, thearrangements of FIGS. 7 and 8 are presented which dispenses with thephoto process in the fabrication of line screen beam-index targetscreens.

Thus, in FIG. 7 a method is illustrated for printing the phosphor stripson substrate or faceplate 11. A jig or fixture 40 holds a plurality ofbrushes which apply, simultaneously, the index material and colorproducing phosphors. Index brush 32 applies the index material, brush34B applies the blue phosphor, brush 36R applies the red phosphor, andbrush 36G applies the green phosphor. All four brushes are held inalignment by fixture 40 which also feeds the phosphor paints to thebrushes. The four strips are guided into register with the rib 18 byroller 42 secured to fixture 40. The use of rib or projection 18 forthis purpose is novel and advantageous. The rib both supports the indexmaterial and guides the brushes to maintain proper alignment andregister of the color producing and index signal producing strips. Whenhigh voltages are to be applied to this target screen a foraminouselectrically conductive mesh may be applied as for example by Saulniersteachings. Alternatively, if a smooth and continuous aluminum layer akinto 22 is desired beneath the index material the brushing is accomplishedin two steps. The brushes 34B, 36R, and 366 deposit the blue, red, andgreen phosphors. The aluminum layer is deposited. Then index brush 32applies the index material. Fixture 40 may apply a single group ofphosphors, or preferably it may apply a plurality of groups of phosphorsby suitably extending its length. In addition to brushing, per se, othermethods of phosphor application may be used such as flame sprayingand/or electrostatic spraying. Also, applicants prior teachings of usinga rollable target screen may be used. In each case, advantage is takenof the guiding feature of ribs or projections 18 to gain properregistration of the strips on the faceplate.

FIG. 8 is akin to FIG. 7 except that fixture 40 is guided by both therib l8 and the faceplate 11. Thus, roller 44 is brought into position atthe corner of rib l8 and the faceplate 11 by spring forces depicted at41 at 43. lndicia 45 on the interior of the faceplate 11 may be used(instead of rib 18) in combination with servocontrol means 62. indicia45 may be electrically conductive frit embedded in or deposited on thefaceplate, or it may be a strip optically distinctive from the surroundof the faceplate. Hence, electrical or optical feelers may be used toguide feedback controlled means 62 in the printing of the phosphorstrips. Typically, the phosphor strips are applied in a thickness ofapproximately 0.001 inches. Accordingly, if the indicia 45 is less thanor not too much greater than 0.001 inches an electrically conductivelayer, comprised of a foraminous mesh, can be mounted directly on thephosphor strips. This provides stabilization of the voltage on thetarget screen and permits the index radiation to be transmittedrearwardly of the target screen to the scintillator detector 6 ofFIG. 1. Indicia 45 may be the index strip itself. Generally, the spraytechnique is preferred to brush application when the target screen isconstructed on a faceplate with a non-flat or spherical surface.

For details on flame spraying, reference is made to Smith U.S. Pat. No.2,861,900, Mondain-Monval U.S. Pat. No. 3,235,700 and lnoue U.S. Pat.No. 3,358,114. For embedding phosphors in a metallic target screen seeHolowaty U.S. Pat. No. 3,177,361. For details on electronic control ofprinting inks and phosphors, reference is made to the AB. Dick CompanyVideojet process and Automation Magazine, page 90, May 1968. TheVideojet process essentially employs a small metal chamber, aboutone-eighth inch in diameter and one-half inch in length, and having anorifice of 0.002 inch to 0.003 inch at one end. If such an assembly isconnected to a source of pressurized ink, it will be discharged throughthe orifice as a non-uniform spray, very much like a garden hose.However, if the assembly is energized by a source of ultrasonic energy,such as a coil driven by an alternating current or-a piezoelectriccrystal, the ink will be discharged from the orifice as a stream ofdroplets of uniform diameter and at a rate equal to the frequency of theenergizing signal. For example, if the assembly is driven at 751(112,the ink stream will comprise 75,000 droplets per second. If the streamis generated through a 0.002 inch orifice, the resulting spot on a pieceof paper will be in the order of 0.0linch in diameter. See also DiproseU.S. Pat. No. 3,404,280 and Loughren U.S. Pat. No. 3,414,221.

Returning to FIGS. 2 and 3, resin layer 9 and implosion panel 8 areadded to the faceplate of the tube as one of the final steps in theproduction of a color kinescope. The properties of panel 8 and layer 9take on additional meaning in a beam-index system. Conventionalfaceplate glass (Coming 9019 clear; 9024 tinted, polished, 40 percenttransmission; 9026 tinted, polished, 50 percent transmission) istransmissive of radiation occupying a narrow region of the ultravioletspectrum from approximately 3,600 4,000 Angstroms. But this is preciselythe wavelength region in which the P-16 phosphor (calcium magnesiumsilicate) radiates in response to electron bombardment; and radiation inthis range of wavelengths excites the scintillator detector 6.

I have observed that even though the target screen is composed of anopaque layer of phosphors and a light reflective aluminum layer ismounted on top thereof that nevertheless a certain amount of visibleradiation is transmitted through the target screen and faceplateassembly. Saulnier estimates the transmission to be, in the order of 3percent. I have not made this measurement. But, 1 have measured theeffects of daylight (and artificial illumination) on the scintillator 6and photodetector 5. The ultraviolet component of this illumination istransmitted through the glass faceplate, the target screen, and thefunnel of the CRT. It strikes scintillator 6 and shows up as randomnoise which masks the index signal in the output of the photodetector.This is most undesirable. Fortunately, there is a simple solution. Ihave found that some of the resin layers conventionally used to bondpanel 8 to faceplate 11 has the exact transmissive properties needed.This resin layer transmits visible radiation above 4,000 Angstroms asdesired, and attenuates the noise generating ultraviolet radiation from3,500 to 4,000 Angstroms. Thus, resin layer 9 performs the additionalimportant function, apparently not heretofore recognized, of blockingundesirable ultraviolet radiation from exciting the plastic scintillator6 disposed rearwardly of the target screen. This improves the signal tonoise ratio in the index circuitry 5 and permits synchronizing thebeam-index circuitry (not shown) with lower electron beam currents. Thisin turn provides or greater contrast and brightness in the reproducedimage. Schwartz U.S. Pat. No. 3,382,393 refers to the resin layer.Alternatively, the faceplate or implosion panel can be made with specialglass to achieve the results of attenuating all optical radiation towhich the scintillator is responsive. Another which scintillator 6 ismade, as the faceplate filter. This material sharply attenuatesultraviolet radiation below 4,000 Angstroms and is highly transmissiveof visible radiation. Indeed, it is this unusual property which enablesscintillator 6 to be used without suffering interference from thevisible content of the picture which is produced on the target screen.

Having described my invention, 1 claim:

1. Alight pipe-scintillator for detecting electromagnetic radiationhaving the shape of a funnel in which the thickness of the wall issubstantially constant over the length of the funnel so that theinterior and exterior sides of the funnel wall can be consideredparallel to each other; whereby optical radiation, generated in theinterior of the funnel wall in response to excitation by the radiationto be detected, is accumulated via light pipe action and concentrated atthe narrow end of the funnel.

2. The device of claim 1 wherein the funnel dimensions are such that theinterior surfaces at the narrow end of the funnel are juxtaposed.

3. The device of claim 1 wherein said light pipescintillator isresponsive to ultraviolet radiation.

4. The device of claim 1 wherein said light pipescintillator isresponsive to ultraviolet radiation of approximately 3,800 Angstromswavelength.

5. An article in accordance with claim 1 wherein the wall has a taperwhich gradually increases the wall thickness towards the narrow end ofthe funnel.

6. The device of claim 5 wherein the funnel dimensions are such that theinterior surfaces at the narrow end of the funnel are juxtaposed.

7. The device of claim wherein said light pipescintillator is responsiveto ultraviolet radiation.

8. The device of claim 5 wherein said light pipescintillator isresponsive to ultraviolet radiation of approximately 3,800 Angstromswavelength.

9. In the method of manufacture of target screens for cathode ray tubes,an efficient and concentrated light source comprising: an ultravioletradiation emitting lamp disposed to emit its radiation upon a sheet ofscintillator material responsive to said radiation thereby to generateoptical radiation which is transmitted in the scintillator via a seriesof internal reflections, said sheet of scintillator also having an edgefrom which the optical radiation emerges thereby to provide aconcentrated source of light.

10. The combination of claim 9 including a second sheet of scintillatormaterial substantially surrounding the ultraviolet responsivescintillator and being responsive to the optical radiation emerging fromthe side walls thereof.

11. The combination of claim 9 wherein the ultraviolet emitting lamp iscylindrical in shape and a major portion of the sheet of scintillator isin the shape of a cylinder surrounding the lamp and spaced therefrom topermit air-cooling.

12. The combination of claim 9 wherein the sheet of scintillator has amajor portion thereof in the shape of a funnel.

13. The combination of claim 12 wherein the shape of the inside narrowend of the funnel is such that the side walls are brought togetherthereby to furnish the light source with a solid area from which theoptical radiation emerges.

14. The combination of claim 12 wherein the walls of the funnel aretapered to increase in thickness at the small end of the funnel.

15. A light source comprising in combination a primary source ofelectromagnetic radiation and a scintillator material responsive theretowherein said scintillator material is (l) positioned to be impinged uponand excited by the primary radiation, (2) is shaped to form at least amajor portion of a thin-walled frusto-conical light pipe, and (3) istransmissive of optical radiation generated in its interior region as aresult of excitation by said primary radiation, whereby said opticalradiation is accumulated via light piping action within said thin-walledlight pipe to emerge at its narrow exit region in concentrated form.

16. The combination of claim 15 wherein the thinwalled light pipe has ataper which gradually increases the wall thickness towards the narrowend thereof.

17. The combination of claim 15 wherein said primary radiation is in theultraviolet region of the spectrum.

18. The combination of claim 15 wherein said primary radiation has anintensity pealgat about 3800 Angstroms wavelength.

19. An elongated scintillator-derived light source comprising incombination a primary source of exciting radiation and a scintillatormaterial responsive thereto wherein said scintillator material (1) has arelatively broad surface area positioned to be impinged upon and excitedby the primary radiation, (2) is shaped to form at least one surface ofa sheet-like light pipe having also at least one relatively narrow exitregion, and (3) is transmissive via light piping action of opticalradiation generated in its interior region as a result of excitation bysaid primary radiation, whereby said optical radiation is accumulatedwithin said sheet-like light pipe to emerge at the relatively narrowexit region thereof in a concentrated and ribbon-like form; said lightpipe being further characterized by a taper which gradually increasesits thickness in the direction of said narrow exit region.

20. The combination of claim 19 wherein said primary radiation is in theultraviolet region of the spectrum.

21. The combination of claim 19 wherein to further increase its capturearea the scintillator material surrounds the primary source of excitingradiation.

22. The combination of claim 19 in the method of manufacture of a linescreen cathode ray tube which includes the feature of using theribbon-like source of light to polymerize selected portions ofphoto-sensitive material thereby to produce strip-like lines on thescreen.

23. In the method of manufacture of line screen faceplates for cathoderay tubes, an efficient and concentrated elongated light sourcecomprising: a primary source of exciting radiation; a relatively broadsheet of scintillator material responsive to said exciting radiation,positioned so as to be impinged upon and penetrated by the excitingradiation over a substantial area thereof; whereby optical radiation,generated inside the broad sheet of scintillator material, istransmitted via a series of internal reflections throughout thescintillator material, said sheet having a relatively narrow exit regionwhich furnishes a concentrated source of light.

24. The combination of claim 23 wherein said broad sheet of scintillatormaterial has a portion thereof which is in the form of a thin-walledhollow cylinder.

25. The combination of claim 24 wherein the source of exciting radiationis an ultraviolet emitting lamp disposed within the thin-walled hollowcylinder.

26. The combination of claim 25 wherein the ultraviolet lamp iselongated and is substantially the same length as the thin-walled hollowcylinder.

27. The combination of claim 23 wherein said primary source emitsultraviolet radiation to which the sheet of scintillator material isresponsive.

28. The combination of claim 23 wherein the broad sheet of scintillatoris tapered so that its thickness increases gradually in the direction inwhich the optical radiation is transmitted towards the narrow exitregion.

29. The combination of claim 23 wherein a plurality of the concentratedand elongated light sources are arranged in a spaced apart array inorder to polymerize selected portions of a photosensitive materialthereby to produce a matching array of strip-like lines on the inside ofthe faceplate of the cathode ray tube.

1. A light pipe-scintillator for detecting electromagnetic radiationhaving the shape of a funnel in which the thickness of the wall issubstantially constant over the length of the funnel so that theinterior and exterior sides of the funnel wall can be consideredparallel to each other; whereby optical radiation, generated in theinterior of the funnel wall in response to excitation by the radiationto be detected, is accumulated via light pipe action and concentrated atthe narrow end of the funnel.
 2. The device of claim 1 wherein thefunnel dimensions are such that the interior surfaces at the narrow endof the funnel are juxtaposed.
 3. The device of claim 1 wherein saidlight pipe-scintillator is responsive to ultraviolet radiation.
 4. Thedevice of claim 1 wherein said light pipe-scintillator is responsive toultraviolet radiation of approximately 3,800 Angstroms wavelength.
 5. Anarticle in accordance with claim 1 wherein the wall has a taper whichgradually increaseS the wall thickness towards the narrow end of thefunnel.
 6. The device of claim 5 wherein the funnel dimensions are suchthat the interior surfaces at the narrow end of the funnel arejuxtaposed.
 7. The device of claim 5 wherein said lightpipe-scintillator is responsive to ultraviolet radiation.
 8. The deviceof claim 5 wherein said light pipe-scintillator is responsive toultraviolet radiation of approximately 3,800 Angstroms wavelength.
 9. Inthe method of manufacture of target screens for cathode ray tubes, anefficient and concentrated light source comprising: an ultravioletradiation emitting lamp disposed to emit its radiation upon a sheet ofscintillator material responsive to said radiation thereby to generateoptical radiation which is transmitted in the scintillator via a seriesof internal reflections, said sheet of scintillator also having an edgefrom which the optical radiation emerges thereby to provide aconcentrated source of light.
 10. The combination of claim 9 including asecond sheet of scintillator material substantially surrounding theultraviolet responsive scintillator and being responsive to the opticalradiation emerging from the side walls thereof.
 11. The combination ofclaim 9 wherein the ultraviolet emitting lamp is cylindrical in shapeand a major portion of the sheet of scintillator is in the shape of acylinder surrounding the lamp and spaced therefrom to permitair-cooling.
 12. The combination of claim 9 wherein the sheet ofscintillator has a major portion thereof in the shape of a funnel. 13.The combination of claim 12 wherein the shape of the inside narrow endof the funnel is such that the side walls are brought together therebyto furnish the light source with a solid area from which the opticalradiation emerges.
 14. The combination of claim 12 wherein the walls ofthe funnel are tapered to increase in thickness at the small end of thefunnel.
 15. A light source comprising in combination a primary source ofelectromagnetic radiation and a scintillator material responsive theretowherein said scintillator material is (1) positioned to be impinged uponand excited by the primary radiation, (2) is shaped to form at least amajor portion of a thin-walled frusto-conical light pipe, and (3) istransmissive of optical radiation generated in its interior region as aresult of excitation by said primary radiation, whereby said opticalradiation is accumulated via light piping action within said thin-walledlight pipe to emerge at its narrow exit region in concentrated form. 16.The combination of claim 15 wherein the thin-walled light pipe has ataper which gradually increases the wall thickness towards the narrowend thereof.
 17. The combination of claim 15 wherein said primaryradiation is in the ultraviolet region of the spectrum.
 18. Thecombination of claim 15 wherein said primary radiation has an intensitypeak at about 3800 Angstroms wavelength.
 19. An elongatedscintillator-derived light source comprising in combination a primarysource of exciting radiation and a scintillator material responsivethereto wherein said scintillator material (1) has a relatively broadsurface area positioned to be impinged upon and excited by the primaryradiation, (2) is shaped to form at least one surface of a sheet-likelight pipe having also at least one relatively narrow exit region, and(3) is transmissive via light piping action of optical radiationgenerated in its interior region as a result of excitation by saidprimary radiation, whereby said optical radiation is accumulated withinsaid sheet-like light pipe to emerge at the relatively narrow exitregion thereof in a concentrated and ribbon-like form; said light pipebeing further characterized by a taper which gradually increases itsthickness in the direction of said narrow exit region.
 20. Thecombination of claim 19 wherein said primary radiation is in theultraviolet region of the spectrum.
 21. The combination of claim 19wherein to fuRther increase its capture area the scintillator materialsurrounds the primary source of exciting radiation.
 22. The combinationof claim 19 in the method of manufacture of a line screen cathode raytube which includes the feature of using the ribbon-like source of lightto polymerize selected portions of photo-sensitive material thereby toproduce strip-like lines on the screen.
 23. In the method of manufactureof line screen faceplates for cathode ray tubes, an efficient andconcentrated elongated light source comprising: a primary source ofexciting radiation; a relatively broad sheet of scintillator materialresponsive to said exciting radiation, positioned so as to be impingedupon and penetrated by the exciting radiation over a substantial areathereof; whereby optical radiation, generated inside the broad sheet ofscintillator material, is transmitted via a series of internalreflections throughout the scintillator material, said sheet having arelatively narrow exit region which furnishes a concentrated source oflight.
 24. The combination of claim 23 wherein said broad sheet ofscintillator material has a portion thereof which is in the form of athin-walled hollow cylinder.
 25. The combination of claim 24 wherein thesource of exciting radiation is an ultraviolet emitting lamp disposedwithin the thin-walled hollow cylinder.
 26. The combination of claim 25wherein the ultraviolet lamp is elongated and is substantially the samelength as the thin-walled hollow cylinder.
 27. The combination of claim23 wherein said primary source emits ultraviolet radiation to which thesheet of scintillator material is responsive.
 28. The combination ofclaim 23 wherein the broad sheet of scintillator is tapered so that itsthickness increases gradually in the direction in which the opticalradiation is transmitted towards the narrow exit region.
 29. Thecombination of claim 23 wherein a plurality of the concentrated andelongated light sources are arranged in a spaced apart array in order topolymerize selected portions of a photosensitive material thereby toproduce a matching array of strip-like lines on the inside of thefaceplate of the cathode ray tube.